1. Field of Invention
The subject invention is related to fuel injectors, in general, and is specifically related to a fuel injector valve controlling and motoring both the air flow and fuel flow into a mixing chamber.
2. Description of the Prior Art
Fuel injector valves are well known mechanisms for controlling the air/fuel ratio of a gasified or atomized fuel-air mixture in an internal combustion engine. Fuel injection was first widely applied to diesel engines where injection of the fuel directly into the cylinder was required. Diesel fuel is heavier and less volatile than gasoline thus very high pressure was needed to properly atomize the fuel. The first automobile gasoline fuel injectors were direct, mechanical fuel injectors developed by Bosch and Mercedes-Benz in the early 1950s. These fuel injectors pumped the fuel either directly into the cylinder or into an intake manifold. High pressure injection pumps, directly driven from the engine, discharged fuel through rigid tubing to the nozzle. The nozzle discharge pressures were about 1500 psi to properly atomize the fuel. The fuel pressure overcame a spring loaded valve in the injector body which eliminated the need for a return fuel line. In the late 1950's Mercedes-Benz began developing a port injection which could use lower fuel pressures, as the injection did not have to overcome combustion chamber pressures. This was first used in the 1957 Mercedes-Benz 300 and port-type injectors have been increasingly used since then.
Early electronic fuel injection systems delivered a pressurized fuel supply (typically 20 to 100 psi) to each injector from a fuel pump which supplied the mechanical energy required for atomization. The injector body contained a solenoid, which when energized, allowed fuel to pass into the nozzle. Although this design has been improved, particularly the controlling electronics, the basic operation has remained the same to this day.
Gianini, U.S. Pat. No. 3,610,213, discloses a fuel injector for minimizing inconsistent air/fuel ratios, pulsations caused by the high frequency of breaks in the fuel stream (caused by the cycling of the injectors), and improper fuel storage in the intake manifold. Gianini's invention consists of a fuel injection system having a separate fuel source, an injector having a fuel reservoir at least as great as the volume of fuel to be injected into the cylinder, a mechanical pump to supply fuel from the fuel source to the injector reservoir, an air source, and a separate pump to supply the air to the injector to atomize the fuel in the reservoir.
Another fuel injector design is disclosed in Sarich U.S. Pat. No. 4,462,776. That patent discloses a method and apparatus for delivering metered quantities of liquid wherein the liquid is circulated through a metering chamber, filling the chamber with the liquid, closing the circulation ports when the metering chamber is full, opening a gas inlet port and a discharge port and admitting gas under pressure through the gas inlet port into the metering chamber and expelling the liquid from the metering chamber to the discharge port. Once the liquid is expelled, the gas inlet port and the discharge ports are closed and the fuel is again circulated through the metering chamber. The amount of liquid in the metering chamber can be regulated only by moving the gas in the port mechanism so as to define a larger or smaller cavity.
An attempt to minimize cycle-to-cycle variation in fuel delivery caused by the buildup of a residual fuel is disclosed in Smith U.S. Pat. No. 4,712,524. Smith discloses that an average thickness of the residual fuel film on the wall of the fuel delivery tube between the metering device and the engine increases as the metered quantity of fuel for delivery increases, when a fixed amount of air is used to convey the fuel through the delivery tube. To resolve this problem, Smith teaches a method of delivering fuel to an internal combustion engine comprising the delivering of individual metered quantities of fuel into a conduit by an individual air pulse, and establishing a secondary gas flow in the conduit to sweep the conduit clean. The secondary gas flow would only occur for part of the time interval between the respective air pulses to deliver the metered quantities of fuel along the conduit. The individual air pulses do not meter the fuel as metering is accomplished using standard metering devices.
The McKay U.S. Pat. No. 5,024,202 discloses a valve structure having a single plunger which includes a first tapered valve for controlling air flow and a second flared valve for delivering the air/fuel mixture. However, this patent does not disclose a method for simultaneously controlling and metering both the air and the fuel into the chamber. The U.S. Pat. No. 5,024,202 describes a solenoid operated fuel injector using a common needle to switch on and off the flows of both fuel and air. The major disadvantage to this system is that both valves open simultaneously, possibly resulting in a danger of poor atomization at the beginning and end of the fuel injection event.
McKay U.S. Pat. No. 4,794,902 discloses a similar solenoid actuated air/fuel metering valve also including a single plunger for implementing various fuel/air mixing injecting steps by metering the air. Again, this patent does not disclose a device for simultaneously metering the air and the fuel into the mixing chamber.
There remains a need to provide for a better atomization of the fuel in internal combustion gasoline engines, particularly under cold start conditions when there is an increased tendency for the fuel to remain unvaporized. Such good quality atomization cannot currently be obtained by conventional electronic atomizers operating at pressures in the region of three times atmospheric pressure. Atomization this good can be obtained with air assisted atomizers, but existing air assisted atomizers have a problem. They require continuous air flow which not only requires an extensive flow of compressed air resulting in a high compressor power requirement, but tend to make the engine run too lean by providing too high an air mix in the air/fuel ratio. Operation using only the pressure difference between the atmosphere and the manifold does not provide sufficiently fine atomization. While electronic fuel injectors are rapidly replacing entirely mechanical injectors because electronic fuel injectors allow greater monitoring of relevant factors and subsequent metering of the fuel and air mixture for combustion, there remains a need to develop a single valve capable of metering both the air and the fuel, to optimize the air/fuel mixture introduced into the manifold or the combustion chamber in order to increase the overall efficiency of the fuel delivery system and to improve related engine performance, especially the control of engine out emissions during cold start. To date, a single valve system which permits both the air and the fuel to be calibrated and precisely metered is not known.